Composition of water glass

2019-06-04 18:14:22

Water glass is a general term for aqueous solutions of various silicates (sodium silicate, potassium silicate, lithium silicate, etc.). Chemical expression:M2O.mSiO2.nH2O

Sodium water glass: 

Sodium water glass is the most commonly used water glass in casting production, also known as "saponin", which is rich in source and cheap. The chemical expression of sodium water glass is Na2O.mSiO2.nH2O, and the expression m is commonly called "modulus", which is the molar ratio of SiO2 to Na2O. The modulus of water glass for casting water glass sand is 1.5~3.0, the mass concentration of water glass is generally 1.3~1.6g/cm3, and the water content n determines the mass concentration of water glass.

Sodium silicate is a weak acid strong base salt, which is a white or off-white agglomerate or powder in the dry state. When dissolved in water, the pure sodium water glass has a colorless viscous liquid and a pH of 11-13. Casting 

water glass usually contains a small amount of impurities (such as ferric oxide, aluminum oxide, calcium oxide, etc.), so its appearance is gray or green

1. Preparation method of sodium water glass, which is prepared by wet method:

The caustic soda (NaOH) solution is heated together with quartz powder or silica sand in a high-pressure (0.5-0.7 MPa) hot reaction vessel with a stirrer to about 160 degrees, and vacuum-filtered or concentrated by evaporation to obtain a finished water. Glass, ie:mSiO2+2 NaOH=Na2O. mSiO2+H2O

The modulus M of the soda water glass produced by the wet process is usually less than 3, which can meet the requirements of the foundry. This process consumes relatively little energy.